Fracture zone identification in the Appalachian fold and thrust belt determined from geophysical logs
The Oak Ridge Reservation (ORR) is located in the Appalachian fold and thrust belt and is comprised of a series of Paleozoic sedimentary rocks that have been structurally duplicated by thrust faulting. All rock units are fractured as a result of the faulting. The fractures are related to medium-scale fault structures (30 to 300 ft(10 to 100 m)) and small-scale (0.5 to 10 in(1 to 20 cm)) deformation of the thrust sheet. Identification and characterization of fracture zones associated with medium-scale faults were accomplished through borehole geophysical techniques. Although the strata on the ORR are pervasively fractured, geophysical log fracture anomalies were primarily associated with medium-scale thrust and tear faults. Estimation of fault displacements suggests that a fracture zone can develop without substantial fault movement. In addition, although a fracture zone can enhance fracture porosity, the associated fault plane may act as a barrier to fluid flow. Investigations showed that a suite of geophysical well logs rather than a single log is essential for fracture zone identification. At the ORR, the borehole televiewer (BHTV), natural gamma ray, and epithermal neutron logs were most useful in fault identification, and the temperature, BHTV, dual induction, and porosity crossplot logs were most useful for fracture zone characterization. 9 refs., 9 figs.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 7036221
- Report Number(s):
- CONF-880583-4; ON: DE89001209
- Resource Relation:
- Conference: International conference on fluid flow in fractured rocks, Atlanta, GA, USA, 15 May 1988; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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